1 /***************************************************************************** 2 * randm.c - Random number generator program file. 3 * 4 * Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc. 5 * Copyright (c) 1998 by Global Election Systems Inc. 6 * 7 * The authors hereby grant permission to use, copy, modify, distribute, 8 * and license this software and its documentation for any purpose, provided 9 * that existing copyright notices are retained in all copies and that this 10 * notice and the following disclaimer are included verbatim in any 11 * distributions. No written agreement, license, or royalty fee is required 12 * for any of the authorized uses. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 ****************************************************************************** 26 * REVISION HISTORY 27 * 28 * 03-01-01 Marc Boucher <marc (at) mbsi.ca> 29 * Ported to lwIP. 30 * 98-06-03 Guy Lancaster <lancasterg (at) acm.org>, Global Election Systems Inc. 31 * Extracted from avos. 32 *****************************************************************************/ 33 34 #include "lwip/opt.h" 35 36 #if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */ 37 38 #include "md5.h" 39 #include "randm.h" 40 41 #include "ppp.h" 42 #include "pppdebug.h" 43 44 #include <string.h> 45 46 #if MD5_SUPPORT /* this module depends on MD5 */ 47 #define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */ 48 49 /*****************************/ 50 /*** LOCAL DATA STRUCTURES ***/ 51 /*****************************/ 52 static char randPool[RANDPOOLSZ]; /* Pool of randomness. */ 53 static long randCount = 0; /* Pseudo-random incrementer */ 54 55 56 /***********************************/ 57 /*** PUBLIC FUNCTION DEFINITIONS ***/ 58 /***********************************/ 59 /* 60 * Initialize the random number generator. 61 * 62 * Since this is to be called on power up, we don't have much 63 * system randomess to work with. Here all we use is the 64 * real-time clock. We'll accumulate more randomness as soon 65 * as things start happening. 66 */ 67 void 68 avRandomInit() 69 { 70 avChurnRand(NULL, 0); 71 } 72 73 /* 74 * Churn the randomness pool on a random event. Call this early and often 75 * on random and semi-random system events to build randomness in time for 76 * usage. For randomly timed events, pass a null pointer and a zero length 77 * and this will use the system timer and other sources to add randomness. 78 * If new random data is available, pass a pointer to that and it will be 79 * included. 80 * 81 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427 82 */ 83 void 84 avChurnRand(char *randData, u32_t randLen) 85 { 86 MD5_CTX md5; 87 88 /* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */ 89 MD5Init(&md5); 90 MD5Update(&md5, (u_char *)randPool, sizeof(randPool)); 91 if (randData) { 92 MD5Update(&md5, (u_char *)randData, randLen); 93 } else { 94 struct { 95 /* INCLUDE fields for any system sources of randomness */ 96 char foobar; 97 } sysData; 98 99 /* Load sysData fields here. */ 100 MD5Update(&md5, (u_char *)&sysData, sizeof(sysData)); 101 } 102 MD5Final((u_char *)randPool, &md5); 103 /* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */ 104 } 105 106 /* 107 * Use the random pool to generate random data. This degrades to pseudo 108 * random when used faster than randomness is supplied using churnRand(). 109 * Note: It's important that there be sufficient randomness in randPool 110 * before this is called for otherwise the range of the result may be 111 * narrow enough to make a search feasible. 112 * 113 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427 114 * 115 * XXX Why does he not just call churnRand() for each block? Probably 116 * so that you don't ever publish the seed which could possibly help 117 * predict future values. 118 * XXX Why don't we preserve md5 between blocks and just update it with 119 * randCount each time? Probably there is a weakness but I wish that 120 * it was documented. 121 */ 122 void 123 avGenRand(char *buf, u32_t bufLen) 124 { 125 MD5_CTX md5; 126 u_char tmp[16]; 127 u32_t n; 128 129 while (bufLen > 0) { 130 n = LWIP_MIN(bufLen, RANDPOOLSZ); 131 MD5Init(&md5); 132 MD5Update(&md5, (u_char *)randPool, sizeof(randPool)); 133 MD5Update(&md5, (u_char *)&randCount, sizeof(randCount)); 134 MD5Final(tmp, &md5); 135 randCount++; 136 MEMCPY(buf, tmp, n); 137 buf += n; 138 bufLen -= n; 139 } 140 } 141 142 /* 143 * Return a new random number. 144 */ 145 u32_t 146 avRandom() 147 { 148 u32_t newRand; 149 150 avGenRand((char *)&newRand, sizeof(newRand)); 151 152 return newRand; 153 } 154 155 #else /* MD5_SUPPORT */ 156 157 /*****************************/ 158 /*** LOCAL DATA STRUCTURES ***/ 159 /*****************************/ 160 static int avRandomized = 0; /* Set when truely randomized. */ 161 static u32_t avRandomSeed = 0; /* Seed used for random number generation. */ 162 163 164 /***********************************/ 165 /*** PUBLIC FUNCTION DEFINITIONS ***/ 166 /***********************************/ 167 /* 168 * Initialize the random number generator. 169 * 170 * Here we attempt to compute a random number seed but even if 171 * it isn't random, we'll randomize it later. 172 * 173 * The current method uses the fields from the real time clock, 174 * the idle process counter, the millisecond counter, and the 175 * hardware timer tick counter. When this is invoked 176 * in startup(), then the idle counter and timer values may 177 * repeat after each boot and the real time clock may not be 178 * operational. Thus we call it again on the first random 179 * event. 180 */ 181 void 182 avRandomInit() 183 { 184 #if 0 185 /* Get a pointer into the last 4 bytes of clockBuf. */ 186 u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]); 187 188 /* 189 * Initialize our seed using the real-time clock, the idle 190 * counter, the millisecond timer, and the hardware timer 191 * tick counter. The real-time clock and the hardware 192 * tick counter are the best sources of randomness but 193 * since the tick counter is only 16 bit (and truncated 194 * at that), the idle counter and millisecond timer 195 * (which may be small values) are added to help 196 * randomize the lower 16 bits of the seed. 197 */ 198 readClk(); 199 avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr 200 + ppp_mtime() + ((u32_t)TM1 << 16) + TM1; 201 #else 202 avRandomSeed += sys_jiffies(); /* XXX */ 203 #endif 204 205 /* Initialize the Borland random number generator. */ 206 srand((unsigned)avRandomSeed); 207 } 208 209 /* 210 * Randomize our random seed value. Here we use the fact that 211 * this function is called at *truely random* times by the polling 212 * and network functions. Here we only get 16 bits of new random 213 * value but we use the previous value to randomize the other 16 214 * bits. 215 */ 216 void 217 avRandomize(void) 218 { 219 static u32_t last_jiffies; 220 221 if (!avRandomized) { 222 avRandomized = !0; 223 avRandomInit(); 224 /* The initialization function also updates the seed. */ 225 } else { 226 /* avRandomSeed += (avRandomSeed << 16) + TM1; */ 227 avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */ 228 } 229 last_jiffies = sys_jiffies(); 230 } 231 232 /* 233 * Return a new random number. 234 * Here we use the Borland rand() function to supply a pseudo random 235 * number which we make truely random by combining it with our own 236 * seed which is randomized by truely random events. 237 * Thus the numbers will be truely random unless there have been no 238 * operator or network events in which case it will be pseudo random 239 * seeded by the real time clock. 240 */ 241 u32_t 242 avRandom() 243 { 244 return ((((u32_t)rand() << 16) + rand()) + avRandomSeed); 245 } 246 247 #endif /* MD5_SUPPORT */ 248 249 #endif /* PPP_SUPPORT */ 250
